The present invention relates to systems and methods for providing advertisements on websites. In an embodiment, a method for providing an advertisement on a website includes obtaining purchase information submitted by a user making a purchase on the website, determining at least one advertisement for a product or service related to the purchase but of a different type than the purchase, and displaying the at least one advertisement on the website when the purchase is completed. In another embodiment, a system for providing an advertisement on a website includes a purchase server, an advertisement source, an analyzer, and an advertisement server.